Negative active material for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

A negative active material for a rechargeable lithium battery, the negative active material including a porous amorphous carbon matrix having a porosity of about 10% to about 64%, silicon oxide distributed in pores of the porous amorphous carbon matrix, and a coating layer on a surface of the porous carbon matrix, the coating layer including an amorphous carbon.

What is claimed is: 
     
         1 . A negative active material for a rechargeable lithium battery, the negative active material comprising:
 a porous amorphous carbon matrix having a porosity of about 10% to about 64%;   silicon oxide distributed in pores of the porous amorphous carbon matrix; and   a coating layer on a surface of the porous carbon matrix, the coating layer comprising an amorphous carbon.   
     
     
         2 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the amorphous carbon matrix comprises a hard carbon matrix or a soft carbon matrix. 
     
     
         3 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the amorphous carbon matrix comprises a hard carbon matrix. 
     
     
         4 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the silicon oxide is SiO x  (where x is about 0.9 to about 2.0). 
     
     
         5 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the porosity of the porous amorphous carbon matrix is about 10% to about 60%. 
     
     
         6 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the silicon oxide has a particle diameter of about 1 nm to about 100 nm. 
     
     
         7 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein an amount of the silicon oxide is about 10 wt % to about 60 wt % based on 100 wt % of the negative active material. 
     
     
         8 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein an amount of the coating layer is about 1 wt % to about 20 wt % based on 100 wt % of the negative active material. 
     
     
         9 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the amorphous carbon in the coating layer comprises soft carbon. 
     
     
         10 . The negative active material for a rechargeable lithium battery as claimed in  claim 1 , wherein the silicon oxide is amorphous silicon oxide. 
     
     
         11 . A method of preparing a negative active material for a rechargeable lithium battery, the method comprising:
 adding a porous amorphous carbon matrix having a porosity of about 10% to about 64% to a liquid silane compound to prepare a mixture;   defoaming the mixture to prepare a defoamed product;   mixing the defoamed product with an amorphous carbon precursor to prepare a mixed product; and   heat-treating the mixed product.   
     
     
         12 . The method of preparing a negative active material for a rechargeable lithium battery as claimed in  claim 11 , wherein the porosity of the porous amorphous carbon matrix is about 10% to about 60%. 
     
     
         13 . The method of preparing a negative active material for a rechargeable lithium battery as claimed in  claim 11 , wherein the amorphous carbon matrix comprises a hard carbon matrix or a soft carbon matrix. 
     
     
         14 . The method of preparing a negative active material for a rechargeable lithium battery as claimed in  claim 11 , wherein the silane compound comprises tetraalkyl orthosilicate, tetraalkoxysilane, silicon tetrachloride, or combinations thereof. 
     
     
         15 . The method of preparing a negative active material for a rechargeable lithium battery as claimed in  claim 11 , wherein the heat-treatment is performed at about 600° ° C.to about 1,000° C. 
     
     
         16 . The method of preparing a negative active material for a rechargeable lithium battery as claimed in  claim 11 , wherein the defoamed product is distributed in a solvent before being mixed with the amorphous carbon precursor. 
     
     
         17 . The method of preparing a negative active material for a rechargeable lithium battery as claimed in  claim 11 , wherein the solvent comprises water. 
     
     
         18 . A rechargeable lithium battery, comprising:
 negative electrode comprising the negative active material of  claim 1 ;   a positive electrode; and   an electrolyte.